How did Kate Middleton get those pearly whites?

What would you do to perfect your smile for the photo seen 'round the world?

We were very impressed when we heard that Kate Middleton chose to do her own makeup for those seen-by-everyone Mario Testino-snapped engagement pics. However, it looks like the princess-to-be has gotten a bit of help - in the dental department, that is.

The Daily Mailreports that Middleton's gorgeous smile underwent a makeover, courtesy of Dr. Didier Fillion, based in offices on London's Wimpole Street.

According to Richard Kay, Kate underwent a "revolutionary dental treatment" to get her teeth picture-perfect ahead of the engagement, only performed by Fillion. He uses 3D digital technology to cut the amount of time braces need to stay on (and also applies the brace behind the teeth to ensure invisibility). Kate probably underwent a teeth whitening as well.

Kate's dental makeover doesn't come cheap, with fees starting at £3,000 for braces on the upper teeth only and £6,000 for upper and lower teeth, with treatment taking from six months to two years. Perhaps Kate's known about this engagement for far longer than any of us suspected...